1. Field of the Invention
This invention relates to diversity reception systems that are applied to base stations of mobile radio communication systems. This application is based on patent application No. Hei 9-170352 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
An example of the conventional diversity reception system is disclosed by the paper of Japanese Patent Application, Publication No. Hei 7-131405, according to which antennas, a number of which is identical to a number of sectors, are used to effect diversity reception. Herein, each of the antennas is designed to have single directivity in transmission of signals and double or more directivity in reception of signals. Now, an outline of operation of the conventional diversity reception system will be described with reference to FIG. 3 and FIG. 4. FIG. 3 shows an example of the diversity reception of three-sector type, wherein an antenna 101 has a transmission/reception radiator for a direction 1001 and a transmission/reception radiator for a direction 1003. As similar to the antenna 101, an antenna 102 has a transmission/reception radiator for a direction 1002 and a transmission/reception radiator for a direction 1001, while an antenna 103 has a transmission/reception radiator for a direction 1003 and a transmission/reception radiator for a direction 1002. FIG. 4 shows detailed configurations following the antennas 101, 102 and 103, wherein there are provided transceivers 111, 112 and 113 as well as transmission/reception distributors 161, 162 and 163. Herein, a receiving input of the antenna 101 is distributed to the transceivers 111 and 113 by means of the transmission/reception distributor 161. Similarly, a receiving input of the antenna 102 is distributed to the transceivers 112 and 111 by means of the transmission/reception distributor 162, while a receiving input of the antenna 103 is distributed to the transceivers 113 and 112 by means of the transmission/reception distributors 163. Diversity reception in the direction 1001 is performed by selection or composition of the receiving input given from the transmission/reception radiator of the antenna 101 and the receiving input given from the transmission/reception radiator of the antenna 102.
The conventional diversity reception system suffers from problems as follows:
Relatively large-scale construction is required because the antennas TV should be fixed separately with each other. Fine sight is spoiled because the antennas themselves relatively stand out.
In the case of the antenna diversity reception using the space diversity, it is preferable to provide a distance corresponding to ten wavelengths or more for an interval between fixing locations of the antennas in order that correlation of electromagnetic waves, received by the antennas respectively, will be canceled. In the conventional diversity reception system, the diversity reception is effected using two antennas out of three antennas, so it is necessary to provide an interval of ten wavelengths or more between fixing locations of the antennas on the same horizontal plane. In the mobile telephone system whose market is rapidly growing these days, for example, such an antenna interval approximately ranges between two and three meters. When fixing the antenna (see FIG. 5), beams 181, which are used for fixing the antennas and each of which has a length of one to two meters, extend horizontally from an upper portion a steel pipe pole 171, so that the antenna is fixed at ends of the beams. Or, as shown in FIG. 6, a ring 182, which is used for fixing the antennas and which has a diameter of two to three meters, is provided at an upper portion of a steel tower, so that the antennas are fixed to the ring. In the above, however, the upper portion of the steel pile pole or the upper portion of the steel tower is heavy in weight. For this reason, it is necessary to provide a relatively large intensity for the steel pipe pole or the steel tower itself, while it is necessary to provide a relatively large intensity for construction foundation of the steel pipe pole or the steel tower. In addition, the antennas occupy relatively broad spaces, so they stand out to spoil the beauty surrounding them.
Another problem is that the conventional diversity reception system requires the transmission/reception distributors 161 to 163, a number of which corresponds to a number of the antennas. So, it is necessary to secure a fixing space for fixing them within the fixed space of the base station device. For this reason, it is hardly possible to narrow the space used for fixing the base station device.
A further problem is that in the conventional diversity reception system, each transceiver requires two receiving amplifiers. For this reason, it is impossible to downsize the system. In FIG. 4, receiving (electric) power input to the transceiver 111 via a transmission/reception terminal 121 is supplied to a receiving power amplifier 141 via a duplexer 131, wherein it is amplified and is then input to a diversity receiver 154. On the other hand, receiving power input to a terminal 124 is amplified by a RPA 142, then, it is input to a diversity receiver 154. The diversity receiver 154 selects one of two inputs thereof or mixes two inputs thereof so as to perform diversity reception. Other transceivers 112 and 113 operate as similar to the transceiver 111 described above. Incidentally, in FIG. 4, xe2x80x9cTPAxe2x80x9d is an abbreviation for xe2x80x9cTransmitting Power Amplifierxe2x80x9d, while xe2x80x9cRPAxe2x80x9d is an abbreviation for xe2x80x9cReceiving Power Amplifierxe2x80x9d.
It is an object of the invention to provide a diversity reception system, which is capable of reducing spaces occupied by multiple antennas fixed to a steel pipe pole or a steel tower.
Thus, it is possible to provide a more economical way for aerial engineering; it is possible to reduce a number of steps for construction of the diversity reception system; and it is possible not to spoil the beauty of the place where the antennas are fixed.
It is another object of the invention to provide a diversity reception system, which is capable of reducing a number of parts that configure a receiving system of the transceiver.
Thus, it is possible to reduce the overall size of the diversity reception system; and it is possible to narrow the space for fixing the system.
A diversity reception system of this invention used for a mobile radio communication system of a sector type is constructed using single-directivity transmitting-receiving antennas and a non-directivity receiving antenna, all of which are fixed to a support pole such as a steel pipe pole and a steel tower. The single-directivity transmitting-receiving antennas are fixed to a peripheral surface of the support pole and are arranged in directions corresponding to sectors respectively. The non-directivity receiving antenna is fixed to a head portion of the support pole and is arranged above the single-directivity transmitting-receiving antennas by a prescribed interval of distance, which corresponds to at least nine wavelengths of radio waves. The single-directivity transmitting-receiving antennas are connected to transceivers respectively. A receiving power amplifier that amplifies receiving power input to the non-directivity receiving antenna is fixed to the support pole and is located just below the antennas so as to compensate a low gain of the non-directivity receiving antenna. A distributor is provided for distributing an output of the receiving power amplifier to the transceivers respectively.
Incidentally, the transceiver is configured by a relatively small number of parts, i.e., a duplexer, a transmitting power amplifier, a receiving power amplifier, a transmitter and a diversity receiver.
Thus, diversity reception is performed using any one of the single-directivity transmitting-receiving antennas and the non-directivity receiving antenna.
Because of the above construction and arrangement of the antennas, it is possible to reduce intervals of distance between the antennas, so it is possible not to spoil the beauty surrounding the facility. In addition, it is possible to reduce the required strength of the support pole. Further, it is possible to reduce a number of parts required for the diversity reception.